Polarity sensitive circuit



Dec. 17, 196-8 HUGH I DRYDEN 3,417,293

DEPUTY ADMINISTRATOR OF THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION POLARITY SENSITIVE CIRCUIT Filed Aug. 11. 1964 LAWQENCE SM/TH INVENTOR.

BY I L 3 X41434; 3I hilu ATTORNEYS United States Patent 3,417,298 POLARITY SENSITIVE CIRCUIT Hugh L. Dryden, Deputy Administrator of the National Aeronautics and Space Administration with respect to an invention of Lawrence S. Smith, Los Angeles, Calif.

Filed Aug. 11, 1964, Ser. No. 388,967 8 Claims. (Cl. 317-1485) The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

This invention relates to a switching circuit and more particularly to a circuit that can be selectively operated to reverse the direction of flow of a current.

One use of a circuit that can change the direction of flow of current is in the operation of a two way magnetic relay. A magnetic relay normally includes an inductance in the form of a solenoid coil and a magnetizable anna-' ture movably carried within the coil. When a pulse of current passes through the coil it creates a force that moves the armature. The direction of current flow through the coil determines the direction of armature movement.

There are many applications for a magnetic relay whose armature is capable of movements in opposite directions. Just as an example, such two-wave movement can be used to move a locking latch to a closed or to an open position. Or, such two-wave movement can be used to remotely control operation of various electrical circuits by making or breaking contacts.

There are a number of ways of accomplishing two-way movement of an armature of a magnetic relay in the prior art. For example one way has been to use two separate power supplies of opposite polarity. In broad terms with two power supplies, one power supply of one polarity is connected to cause current to move the armature in one direction. And, the other power supply of opposite polarity is connected to move the armature in the opposite direction.

v One disadvantage of the above construction is that it is expensive to provide two power supplies. It is also expensive to supply the associated circuit components needed by two power supplies. In addition the more components that are used the greater the chance for some of them to fail. Also with two power supplies it is relatively difficult to control operation of the circuit.

Another example of a construction for providing twoway movement of an armature of a magnetic relay is to simply use two independent and separate circuits and two separate solenoid coils for the armature. In this construction, each coil is arranged to move the armature in one direction. That is, when current flows through one coil, it is energized and will move the armature in one direction. When the flow of current is through the other coil it in turn is energized and will move the armature in the opposite direction.

This construction also has disadvantages like the construction described above. It is expensive to provide two solenoid coils. It is also expensive to provide the associated circuit components needed to operate two solenoid coils independently. And it is also relatively ditiicult to control operation of these two independent circuits.

In general terms, this invention includes a circuit with one power supply connected to place equal charges on 3,417,298 Patented Dec. 17, 1968 two capacitances connected in parallel. The capacitances are connected to have a discharge path in a selected direction through a solenoid coil of a magnetic relay to provide bi-directional movement of the armature.

The direction in which a capacitance discharges through the coil is controlled by a first and second switch means. One switch means is closed only by a control signal voltage of positive polarity. The other switch means is closed only by a control signal voltage of negative polarity.

With the above construction, any voltage source capable of providing pulses of negative and positive polarity can control the bi-directional movement of the armature. That is, when a control voltage pulse of positive polarity is applied to the circuit, it will close one switch means, while the other switch means remains open. The closed switch means establishes a discharge path for a selected capacitance so that it discharges through the solenoid coil in one direction. If on the other hand, a controlvoltage pulse of negative polarity is applied to the circuit it will only close the other switch means. This switch means will establish a different discharge path for the other capacitance so that it discharges through the solenoid coil in the opposite direction.

It is therefore a principal object of this invention to provide a circuit that can be selectively operated to change the direction of flow of current.

Another object of this invention is to provide a circuit useable with a magnetic relay that provides bi-directional movement of the armature of the relay while using only one power supply and one solenoid coil.

Another object of this invention is to provide a circuit that can be controlled by one signal source to selectively shift the armature of a magnetic relay to provide bi-directioned operation.

Other objects and advantages will appear from the fol.- lowing detailed description considered in conjunction with the accompanying drawings, wherein:

FIG. 1 is a circuit diagram of a preferred embodiment of the invention; 7

FIG. 2 is a schematic showing of an equivalent circuit of FIG. 1 to illustrate the passage of current when one switch means is closed; and

FIG. 3 is similar to FIG. Zshowing the passage of the current when the other switch means is closed.

DESCRIPTION For purposes of illustration, a preferred embodiment of the invention is shown in FIG. 1 with respect to its use in the bi-directional operation of a magnetic relay 2.

A magnetic relay broadly includes an armature 4 movably carried within a solenoid coil 6 and movable in the direction of arrows 7 and 8. The armature in turn may be provided with contacts (not shown) to make or break contacts of control circuits, as is well known in the art.

The circuitry shown in FIG. 1 can provide two-way movement of armature 4 of magnetic relay 2. In the explanation of the circuit, where current is referred to, it is electron flow that is meant. v

Essentially the circuit includes a pi-network made up of two capacitances C1 and C2 having an inductance or solenoid coil 6 electrically connected between them. The capacitances C1 and C2 form the legs of the network and are connected to each end of coil 6 by conductors 10 and 12. v

Capacitances C1 and C2 are charged by a source of di rect current that may for example be a direct current battery B-lof 25 volts. The ground of the battery is indicated at 14. and it is connected to conductor 16.

capacitances C1 and C2 have connected in parallel with them a first switch means indicated by dotted lines 18. This switch means is adapted to be closed by a control voltage pulse V1 of positive polarity applied at terminals 20 and 22. The capacitances also have connected in parallel with them a second switch means indicated by dotted lines 24. This switch means is adapted to be closed by a control voltage pulse V1 of negative polarity applied at terminals 20 and 22.

Switch means 18 includes a voltage controlled diode switch 26, more commonly referred to as a silicon controlled rectifier, and an NPN transistor 28. Transistor 28 passes a positive pulse signal V1 and in-turn closes or opens diode switch 26 to the flow of current. i

, Diode switch 26 has its anode connected through resistance 32 to B+. The cathode of diode switch 26 is connected to resistance 34 and resistance 34 is in turn connected to ground 14 through conductor 16. Resistance 34 serves to limit current through diode switch 26.

Transistor 28 has its emitter connected to diode switchs' gate 36 by conductor 38. Also connected to conductor 38 is resistance 40 whose other end is connected to conductor 16 and to terminal 22. Resistance 32 is made large to prevent either switch 18 or 24 from remaining on. Transistor tively generate a positive and negative polarity voltage pulse in a random or selected order is suitable for use with the circuit. The control means to generate voltage pulses V1, is not part of the invention and its selection would depend primarily on the type of armature movement wanted. As an example a computer can be used for the source of voltage pulse.

Voltage pulse V1 in addition to being-applied to transistor 28, is also applied through conductor 46 to the negative polarity controlled switch means 24. Diodes switch means'24 also controls operation of'capacitances C1 and C2.

.Switch means 24 includes voltage controlled diode switches 48 and 50, and current limiting resistors 52 and 54..Diode switches 48 and'50 are commonly known as Schockly or'f our layer diodes. Diode switch 48 is connected to resistance 52 and these are in shunt across capacitance C2. Diode switch 50 is connected to resistance 54 and these are in parallel to resistance 52.

Diode switch 48 has its cathode connected through conductor 46 to'the anode of diode switch 50. Diode switch 48 is connected to conductor 12 which is connected to coil 6 and capacitance C2. Resistances 52 and 54 are connected through conductor 16 to ground 14.

, Resistance ,52 is madevery large compared to transistor base resistance 44. This is to prevent the positive polarity signal current from by-passing transistor base resistance 4 OPERATION The circuit operates in the following manner:

CHARGING Capacitances C1 and C2 are charged by direct current source B+. The path of the charging current in the case of capacitance C1 being from ground 14, through capacitance C1, resistance 32 and then to B+. In the case of capacitance C2 the path of the charging current is from ground 14, through capacitance C2, coil 6, resistance 32 and then to B+.

7 Resistance 32 in the charging circuit of capacitance C2 also functions to establish a time constant that will prevent capacitance C2 from charging too rapidly, otherwise the impulse of current passing through solenoid coil 6, while capacitance C2 is charging, might accidentally shift armature 4.

POSITIVE POLARITY PULSE To move armature 4 in a first direction control signal means 45 is operated to provide a control voltage pulse V1 of positive polarity at input terminals 20-22. Current will flow through resistance 44 connected to the base of NPN transistor 28 to generate a positive voltage that in turn will turn the transistor on.

When transistor 28 is on, current flows from ground 14 through resistance 40, then through the emitter and collector of the transistor, through resistance 42 and then to B+. The flow of current through resistance 40 in effect closes diode switch 26. The current makes the upper part of resistance 40 relatively more positive. This positive voltage is in turn applied by conductor 38 to gate 36 of 4 diode switch 26 and will close this diode switch so it will conduct. a

When switch 26 is closed, a discharge path is provided for capacitances C1 and C2. Capacitance C1 will quickly discharge through resistance 34, diode switch 26 and then back to the other plate of the capacitance an shown in FIG. 2 of the drawings.

Capacitance C2 will discharge more slowly than capacitance C1 since it has coil 6 in itsdischarge path. Capacitance C21will discharge both through discharge. diode I switch 26 and also through capacitance C1, to provide a high impulse of current shown by arrow 7 in FIG. 2 through coil or impedance 6. This high current will in turn move armature 4, in a first direction.

NEGATIVE POLARITY PULSE. To move armature 4 in the opposite direction, control signal means 45 is operated to provide a control voltage pulse V1 of negative polarity at input terminals 20, 22.

for capacitances C1 and C2. Capacitance C2 will discharge 44. That is, if resistance 52 were small compared to resistance .44, then on a positive polarity signal, the majority of current would flow from ground 14, through conductor 16, resistance 52, conductor 46, and then to terminal 20;

instead of through transistor base resistance 44 where it" is desired to develop a high voltage to turn transistor through resistance 52, diode switch 48 and back to the other plate of the capacitance as shown in FIG. 3.

However since resistance 52 is very large it is desirable that the capacitances discharge through a small resistance so less power will be used. To accomplish this, diode.

switch 50 and small resistance 54, become operative. As current flows upward through resistance 52 it makes the top of the resistancemore positive. This positive voltage is in turn applied to the annode of diode switch 50 and closes diode switch 50 so that it now conducts.

When diode switch 50 closes, it creates a rapid discharge tance C2 since it now has coil 6 in its path. Capacitance C1 will discharge both through diode switch 50 and also through capacitance C2 to provide a high impulse of current shown by arrows 8 in FIG. 3, through coil 6. This high current Will move armature 4 in a reverse direction. It will be noted that when a positive polarity voltage pulse V1 is applied at terminals 20' and 22 the pulse is also applied by conductor 46 to the anode of diode switch 50. As a matter of design therefore, diode switch 50 must be selected with a high enough voltage rating so that it does not break down and conduct on the positive pulse.

With the above circuit construction it will be noted that there are a number of advantages:

First, only one power supply and only one solenoid coil 6 are required;

Second, it will be noted that the circuit uses very little power and is normally dormant. The circuit will use power only after the voltage pulses are applied. Until then only leakage current will flow in the circuit;

Third, the circuit is very simple and requires very few components;

Fourth, very low voltage pulses are required to switch the circuits, and

Fifth, as would be obvious to one skilled in the art, the sensitivity of the circuit can be increased by component selection and introducing gain stages at the input. Also, the polarity of the circuit could be reversed as is well known in the art. 7

It should be understood that it is not intended to limit this invention to the herein disclosed form, but that the invention should include such other forms or modifications as may be embraced by the scope of the appended claims.

What is claimed is: 1. In a circuit for providing impulses of current through an impedance in selected directions, the combination comprising:

an impedance; first switch means having two input terminals, said switch means being connected to said impedance and operative in response only to a voltage pulse of positive polarity on said terminals to provide an impulse of current through said impedance in a first direction; and second switch means having the same two input terminals, said second switch means also being connected to said impedance and being operative only in response to a voltage pulse of negative polarity on said terminals to provide an impulse of current through said impedance in a direction opposite to said first direction said first and second switch means being constructed to operate in random order depending on the sequence and polarity of the voltage pulses applied to said two input terminals. 2. In a circuit for providing impulses of current through an inductance in selected directions, the combination comprising:

an inductance; a source of direct voltage; first and second capacitances, said capacitances and said inductance being connected in the form of a pi-network, with said capacitances, being connected to said direct voltage source to become charged during the application of voltage from said source;

first switch means connected to said capacitances and to said inductance, said first switch means having input terminals, said first switch means being operative in response to a first signal applied to said input terminals to establish a discharge path through said inductance for one of said capacitances to provide an impulse. of current in a first selected direction;

' and second switch means connected to said capacitances and to said inductance, said second switch means being connected to the same input terminals as said first switch means, and being operative in response to a different signal than said first signal applied to said input terminals to establish a discharge path through said inductance in the reverse direction for the other of said capacitances to provide an impulse of current in a direction opposite to said first direction. 3. In a circuit for providing impulses of current through an inductance in selected directions, the combination comprising:

an inductance; a source of direct voltage; first and second capacitances, said capacitances and said inductance being connected in the form of a pi-network, said capacitances being coupled in parallel to said direct voltage source to become charged during the application of voltage from said source;

first switch means connected to said capacitances and to said inductance, said first switch means having input terminals and being operative in response to a voltage pulse of positive polarity applied to said input terminals to establish a discharge path through said inductance for one of said capacitances, to provide a high impulse of current in a first selected direction; and second switch means connected to said capacitances and to said inductance, said second switch means, being connected to the same input terminals as said first switch means and being operative in response to a voltage pulse of negative polarity applied to said input terminals to establish a discharge path through said inductance for the other of said capacitances, to provide a high impulse of current in a direction opposite to said first direction. 4. In a circuit for providing impulses of current through an inductance in selected directions, the combination comprising:

an inductance; a source of direct voltage; first and second capacitances, said capacitances and said inductance being connected in the form of a pi-network said capacitances being coupled in parallel to said direct voltage source to become charged during the application of voltage from said source;

first switch means including a voltage controlled diode switch having its cathode connected to one plate of each of said capacitances and its anode connected to the other plate of said first capacitance, and its anode also connected to the other plate of said second capacitance through said inductance, said first switch means having input terminals and being operative in response to a voltage pulse of positive polarity applied to said input terminals to close said voltage controlled diode switch to establish a discharge path through said inductance for said second capacitance, to provide a high impulse of current in a first selected direction; and

second switch means including a voltage controlled diode switch having its cathode connected to one plate of each of said capacitances and its anode connected to the other plate of said second capacitance and its anode also connected to the other plate of said first capacitance through said inductance, said second switch means being connected to the same input terminals as said first switch means and being operative in response to a voltage pulse of negative polarity applied to said input terminals to close said voltage controlled diode switch to establish a discharge path through said inductance to provide a high impulse of current in a direction opposite to said first direction.

'5. In a circuit for providing impulses of current through an inductance in selected directions, the combination comprising:

an inductance;

3,417,298 7 8 a source of direct voltage; said inductance for said first capacitance and profirst and second capacitances, said capacitances and vide a high impulse of current in a direction opposite said inductance being connected in the form of pito said first direction. network, said capacitances being coupled in parallel 7. In a, circuit for providing impulses of current to said direct voltage source to become charged durthrough an inductance in selected directions, the combinaing the application of voltage from said source; tion comprising: first switch means including a first voltage controlled an inductance;

' switch having one end'connected to one plate of each a source of direct voltage;

of said capacitances and its other end connected to first and second capacitances, said capacitances and the other plate of said capacitance, and its other end establish a discharge path through said inductance for said first capacitance to provide a highimpulse of current in a direction opposite to said first direction.

said inductance being connected in the form of 21 pialso connected to the other plate of said second ca- 10 network, said capacitances being coupled in parallel pacitance through said inductance, said first switch vto said direct voltage source to become charged meanshaving input terminals and being operative in during the application of voltage from said source;

response to a voltage pulse of positive polarity apfirst switch means including a first voltage controlled plied to said input terminals to close said first voltdiode switch having its cathode connected to one age controlled switch toestablish a discharge path plate of each of said capacitances and its anode through said inductance for said second capacitance connected to the other plate of said first capacitance, to provide a high impulse of current in a first selected and its anode also connected to the other plate of direction; and a said second capacitance through said inductance, a second voltage controlled switch having one end consaid first switch means having input terminals and nected to one plate of each of said capacitances being operative in response to a voltage pulse of through a resistance, and its other end connected to positive polarity applied to said input terminals to the other plate of said second capacitance, and said close said diode switch to establish a discharge path other end also being connected to the other plate of through said inductance for said second capacitance said first capacitance through said inductance, said and provide a high impulse of current in a first resistance being connected to the same input terselected direction. minals as said first switch means and being operative second voltage controlled 'diode switch including a in response to a voltage pulse of negative polarity high resistance, said second switch having its cathode applied across said resistance by said input terminals connected to one plate of each of said capacitances to close said second voltage controlled switch to through said high resistance and its anode connected to the other plate of said second capacitance, andits anode also connected to the other plate of said first capacitance through said inductance, said high resistance being connected to the same input terminals 6. In a circuit for providing impulses of current through an inductance in selected directions, the combination comprising:

as said first switch means and being operative in response to a voltage pulse of negative polarity applied across said high resistance by said input terminals an inductance; to generate a voltage that closes said second voltage a source of direct voltage; controlled diode switch; and

first second capacitances, Said c pacitances and a third voltage controlled diode switch of low resistsaid indutance being connected in the form of a pinetwork, said capacitances being coupled in parallel to said direct voltages source to become charged during the application of voltage from said source;

ance in parallel with said high resistance, said third switch being operative in response to current flow through said high resistance to shunt said high resistance to establish a low resistance discharge path first switch means including a first voltage controlled switch having one end connected to one plate of each of said capacitances and its other end connected to posite to said first direction.

the other plate of said first capacitance, and its other 8. In a circuit for providing impulses of current end also connected to the other plate of said second through an inductance in selected directions, the comcapacitance through said inductance, said first switch bination comprising: means having input terminals and being operative an inductance; I

in response to a voltage pulse of positive polarity a source of direct voltage;

applied to said input terminals to close said first first and second capacitances, said capacitances and through said inductance for said first capacitance and provide a high impulse of current in a direction opvoltage'controlled switch to establish a discharge said inductance being connected in 'the form of a pipath through said inductance for said second capacinetwork, said capacitances being coupled in parallel tance and provide a high impulse of current in a to said direct voltage source to become charged first selected direction; during the application of voltage from said source;

a second voltage controlled switch including a reSiSta first voltage controlled diode switch having its cathode ance, said second switch having its one end conconnected to each of said capacitances and its anode nected to one plate of each of said capacitances 0 connected to the first of said capacitances, and its through a high resistance and its other end conanode also connected to said second capacitance nected to the other plate of said second capacitance, through said inductance; and its other end also connected to the other plate an NPN transistor having its emitter and collector of said first capacitance through said inductance, said connected in series with said source of direct current high resistance being connected to the same input 5 and in parallel with said first diode switch, the emitterminals as said first switch means and 'being'operater and base of said transistor having input tertive in response to a voltage pulse of negative polarity minals and operative in response" to a voltage 'pulse applied across said high resistance by said input terof positive polarity applied to said input terminals minals to close said second voltage controlled switch; to turn said transistor on and close said first diode and a switch to establish a discharge path through said a third voltage controlled switch of low resistance in inductance for said second capacitance, and provide parallel;with said high resistance, said third switch a high impulse of current in a first selected direcbeing operative to shunt sad high resistance in retion; a

sponse to current flow through said high resistance, a second voltage controlled diode switch including a to establish a low resistance discharge path through large resistance, said second switch having its cathode 3,417,298 9 10 connected to each of said capacitances through a resistance discharge path through said inductance for large resistance and its anode connected to the secsaid first capacitance d provide a high impulse of 0nd of said capacitances, and to its anode also connected to said first capacitance through said inductance, said high resistance being connected to the 5 References Cit d same input terminals as said transistor and being UNITED STATES PATENTS operative in response to a voltage of negative polarity current in a direction opposite to said first direction.

applied across said high resistance by said input ter- 3,125,759 3/ 1964 Klein et 317148 minals to close said second voltage controlled diode 3,021,454 2/1964 PICFeHS 317-151 witch; and 10 Elliott a third low resistance voltage controlled diode switch in parallel with said high resistance, and operative LEE Pmnary Exammer' in response to current flow through said high resist- US. Cl. X.R. ance to shunt said high resistance, to establish a low 151 

1. IN A CIRCUIT FOR PROVIDING IMPULSES OF CURRENT THROUGH AN IMPEDANCE IN SELECTED DIRECTIONS, THE COMBINATION COMPRISING: AN IMPEDANCE; FIRST SWITCH MEANS HAVING TWO INPUT TERMINALS, SAID SWITCH MEANS BEING CONNECTED TO SAID IMPEDANCE AND OPERATIVE IN RESPONSE ONLY TO A VOLTAGE PULSE OF POSITIVE POLARITY ON SAID TERMINALS TO PROVIDE AN IMPULSE OF CURRENT THROUGH SAID IMPEDANCE IN A FIRST DIRECTION; AND SECOND SWITCH MEANS HAVING THE SAME TWO INPUT TERMINALS, SAID SECOND SWITCH MEANS ALSO BEING CONNECTED TO SAID IMPEDANCE AND BEING OPERATIVE ONLY IN RESPONSE TO A VOLTAGE PULSE OF NEGATIVE POLARITY ON SAID TERMINALS TO PROVIDE AN IMPULSE OF CURRENT THROUGH SAID IMPEDANCE IN A DIRECTION OPPOSITE TO SAID FIRST DIRECTION SAID FIRST AND SECOND SWITCH MEANS BEING CONSTRUCTED TO OPERATE IN RANDOM ORDER DEPENDING ON THE SEQUENCE AND POLARITY OF THE VOLTAGE PULSES APPLIED TO SAID TWO INPUT TERMINALS. 